Balloon catheter having metal balloon and method of making same

ABSTRACT

A metal balloon catheter having a main tubular body, a metal balloon proximate a distal end of the main tubular body, a central annulus extending along an entire longitudinal aspect of the catheter for accommodating a guidewire therethrough and an inflation annulus adjacent the central annulus which extends along the longitudinal axis of the main tubular body and terminates in fluid flow communication with an inflation chamber of the metal balloon. The metal balloon catheter may be either unitary integral metal catheter in which the main tubular body and the balloon are fabricated of metal, or it may consist of a polymeric main tubular body and a metal balloon.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation of co-pending commonlyassigned U.S. Ser. No. 10/135,582 filed Apr. 29, 2002, which relates toand claims priority from U.S. Provisional Patent Application Serial No.60/309,406 filed Jul. 31, 2001, and is a continuation-in-part of U.S.patent application Ser. No. 09/433,929 filed Nov. 19, 1999, issued asU.S. Pat. No. 6,379,383 issued Apr. 30, 2002.

BACKGROUND OF THE INVENTION

[0002] The present invention relates generally to balloon catheters andmore specifically to balloon catheters suitable for use in stentdelivery, perfusion, drug delivery, angioplasty, valvuloplasty andendartherectomy procedures. More particularly, the present inventionpertains to a balloon catheter having a balloon fabricated solely ofmetal and to a method of making metal balloons.

SUMMARY OF THE INVENTION

[0003] It is an object of the present invention to provide a ballooncatheter having a metal balloon. It is a further objective of thepresent invention to provide a method of making a balloon catheterhaving a metal balloon. The inventive metal balloon catheter consistsgenerally of a catheter comprising a main tubular body, a metal balloonproximate a distal end of the main tubular body, a central annulusextending along an entire longitudinal aspect of the catheter foraccommodating a guidewire therethrough and an inflation annulus adjacentthe central annulus which extends along the longitudinal axis of themain tubular body and terminates in fluid flow communication with aninflation chamber of the metal balloon. The metal balloon catheter mayconsist of a unitary integral metal catheter in which the main tubularbody and the balloon are fabricated of metal, or it may consist of apolymeric main tubular body and a metal balloon. As with conventionalballoon catheters, the inventive metal balloon catheter has standardconnectors for coupling conventional balloon catheter accessories.

[0004] The inventive metal balloon may assume a wide variety ofgeometries, including without limitation, tubular coils such as for usein endartherectomy procedures or as perfusion balloons, bifurcatedballoons for angioplasty of vascular bifurcations or for delivery ofbifurcated implantable devices, and angled balloons that have an angularoffset from the longitudinal axis of the catheter. Additionally, becausethe inventive metal balloon is fabricated of metal, it may be made moreor less radiopaque by fabricating the balloon of a radiopaque metal,such as tantalum, or providing regions on the balloon that have aradiopaque metal differentially incorporated thereupon. Moreover, theinventive metal balloon may be used either as a conductor of directlyapplied electrical energy or inductively energized by externalapplication of energy, such as by ultrasound or magnetic resonance. Thisconductive property of the inventive metal balloon is particularlyuseful in diathermy, to return a signal for imaging without an addedcontrast medium, or return a signal to provide data concerning the invivo environment.

[0005] The inventive metal balloon is preferably fabricated of abiocompatible metal and is formed as a film of material. The inventivemetal balloon is not restricted to single layer films, but a pluralityof films may be laminated to one another in order to enhance thematerial, geometric and/or functional properties of the resultant metalballoon. Suitable materials to fabricate the inventive metal balloon arechosen for their biocompatibility, mechanical properties, i.e., tensilestrength, yield strength, and their ease of deposition, include, withoutlimitation, the following: titanium, vanadium, aluminum, nickel,tantalum, zirconium, chromium, silver, gold, silicon, magnesium,niobium, scandium, platinum, cobalt, palladium, manganese, molybdenumand alloys thereof, such as zirconium-titanium-tantalum alloys, nitinol,and stainless steel.

[0006] The inventive metal balloon is preferably fabricated by vacuumdeposition techniques. In accordance with the present invention, thepreferred deposition methodologies include ion-beam assisted evaporativedeposition and sputtering techniques. In ion beam-assisted evaporativedeposition it is preferable to employ dual and simultaneous thermalelectron beam evaporation with simultaneous ion bombardment of thesubstrate using an inert gas, such as argon, xenon, nitrogen or neon.Bombardment with an inert gas, such as argon ions serves to reduce voidcontent by increasing the atomic packing density in the depositedmaterial during deposition. The reduced void content in the depositedmaterial is one of the important factors that allow the mechanicalproperties of that deposited material to be similar to the bulk materialproperties. Deposition rates up to 20 nm/sec are achievable using ionbeam-assisted evaporative deposition techniques.

[0007] With the sputtering technique, it is preferable to employ acylindrical sputtering target, a single circumferential source whichconcentrically surrounds the substrate which is held in a coaxialposition within the source. Other source geometries, includingspherical, are also contemplated to best coat substrates with complexgeometries including the inventive balloon. Alternate depositionprocesses which may be employed to form the metal balloon in accordancewith the present invention are cathodic arc, laser ablation, and direction beam deposition. When employing vacuum deposition methodologies, thecrystalline structure of the deposited film affects the mechanicalproperties of the deposited film. These mechanical properties of theentire deposited film or differential section of the deposited film maybe modified by post-process treatment, such as by, for example,annealing, high pressure treatment or gas quenching.

[0008] During deposition, the chamber pressure, the deposition pressureand the partial pressure of the process gases are controlled to optimizedeposition of the desired species onto the substrate. As is known in themicroelectronic fabrication, nano-fabrication and vacuum coating arts,both the reactive and non-reactive gases are controlled and the inert ornon-reactive gaseous species introduced into the deposition chamber aretypically argon and nitrogen. The substrate may be either stationary ormoveable, either rotated about its longitudinal axis, or moved in an X-Yplane within the reactor to facilitate deposition or patterning of thedeposited material onto the substrate. The deposited material maybedeposited either as a uniform solid film onto the substrate, orpatterned by (a) imparting either a positive or negative pattern ontothe substrate, such as by etching or photolithography techniques appliedto the substrate surface to create a positive or negative image of thedesired pattern or (b) using a mask or set of masks which are eitherstationary or moveable relative to the substrate to define the patternapplied to the substrate. Patterning may be employed to achieve regionsof the metal balloon that exhibit different functional properties, suchas providing folding regions that permit low profile folding of themetal balloon for endoluminal delivery, or different geometricproperties of the metal balloon, such as recesses in the surface of themetal balloon having mating geometries for nesting a stent. Complexfinished geometries and material properties of the resultant metalballoon, both in the context of spatial orientation of the pattern,material thicknesses at different regions of the deposited film, ordifferences in the crystalline structure of the metal film at differentregions of the metal film may be accomplished by employing vacuumdeposition techniques and post-process heat treatment of the metal film.

[0009] These and other objectives, features and advantages of thepresent invention will become more apparent to those of ordinary skillin the art from the following more detailed description of the presentinvention taken with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE FIGURES

[0010]FIG. 1 is a perspective view of the inventive metal ballooncatheter.

[0011]FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1.

[0012]FIG. 3 is a cross-sectional view of a drug delivery metal ballooncatheter embodiment.

[0013]FIG. 4 is a perspective view of a perfusion metal balloon catheterembodiment.

[0014]FIG. 5 is an elevational view of an embodiment of a metal balloonsurface topography.

[0015]FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 5.

[0016]FIG. 7 is a cross-sectional view of a metal balloon embodimenthaving an elastomeric coating applied thereto.

[0017]FIG. 8 is a photograph of the inventive metal balloon catheter.

[0018]FIG. 9 is a photograph of the inventive metal balloon catheterunder x-ray imaging.

[0019]FIG. 10A is a perspective view of the inventive metal balloon inits inflated state.

[0020]FIG. 10B is a perspective view of the inventive metal balloon inits deflated state in accordance with one embodiment of the invention.

[0021]FIG. 10C is an end view of the inventive metal balloon in itsdeflated state.

[0022]FIG. 10D is an end view of the inventive metal balloon in itsdeflated state being folded in accordance with one embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] With particular reference to FIGS. 1-2, the inventive metalballoon catheter 10 consists generally of a primary tubular catheterbody member 12 and a balloon 14 situated at a distal end of the metalballoon catheter 10. A proximal end of the metal balloon catheter 10(not shown) is provided with conventional fittings to couple withconventional balloon catheter control accessories. The body member 12and the balloon 14 may both be fabricated of biocompatible metal and/ormetals, which may be selected from the group consisting of titanium,vanadium, aluminum, nickel, tantalum, zirconium, chromium, silver, gold,silicon, magnesium, niobium, scandium, platinum, cobalt, palladium,manganese, molybdenum and alloys thereof, such aszirconium-titanium-tantalum alloys, nitinol, and stainless steel.Alternatively, the body member 12 may be fabricated of a biocompatiblepolymer and only the balloon 14 is fabricated of a biocompatible metal,and affixed to the body member 12 using a suitable biocompatibleadhesive.

[0024] With each of the embodiments of the present invention describedherein, the metal balloon 14 may consist of a single layer of a singlemetal, multiple layers of a single layer or a multiple layers ofmultiple metals. With a laminated structure, the metal balloon 14 mayinclude one or more radiopaque metals to enhance visualization of themetal balloon 14 under x-ray.

[0025] The balloon 14 is coaxially positioned about the body member 12and defines an inflation lumen 16 between an inner wall of the balloon14 and the body member 12. As with conventional balloon catheters, thebody member 12 is a tubular member and includes an inflation lumen 20that communicates between the proximal end of the body member 12 and atleast one inflation port 22 in fluid flow communication with theinflation lumen of the balloon 14. The inflation lumen 20 may alsofunction as a guidewire lumen, or a discrete guidewire lumen 18 may beprovided in the body member 12.

[0026] Conventional balloon catheters typically require a large numberof inflation ports 22 in order to meet governmental regulatoryrequirements for inflation and deflation times. However, it has beenfound with the present invention, that by fabricating the balloon 14 ofa biocompatible metal having a wall thickness between 0.1μ and 25μ andinflated outer diameters between 0. 1 mm and 40 mm, that the regulatoryrequirements for inflation and deflation times may be met with a singleinflation port 22.

[0027] By fabricating the balloon 14 of a biocompatible metal, wallthicknesses between 3μ and 12μ may be achieved, with the resulting metalballoon 14 exhibiting zero compliance with extremely high tensilestrength. An additional advantage resulting from the inventive metalballoon 14 is that certain metals, such as nitinol, exhibit lubricioussurface properties which eliminates the need for surface lubricantsfound with conventional polymeric balloons. Furthermore, in theembodiment where the inventive metal balloon is made from a superelasticmaterial such as nitinol, the metal balloon may be fabricated such thatthe low profile configuration is associated with lowest strain state ofthe balloon such that after inflation the balloon reassumes the lowprofile configuration under its own superelastic properties. In theembodiment where the inventive metal balloon is made from a shape memorymaterial such as nitinol, the metal balloon may be fabricated such thatthe low profile configuration is associated with lowest strain hightemperature state of the balloon such that after inflation the balloonreassumes the low profile configuration upon the application of heat.

[0028] Turning to FIG. 3 there is illustrated a drug delivery embodiment30 of the inventive metal balloon catheter. The inventive drug deliverymetal balloon catheter 30 consists generally tubular catheter bodymember 32 defining an inflation lumen 33 and communicating with at leastone inflation port 34, a first metal balloon 36 and a second metalballoon 38 in coaxial, spaced-apart concentric relationship with one andother, and an annular lumen 42 intermediate the first metal balloon 36and the second metal balloon 38, which is in fluid flow communicationwith an introductory lumen 46. The second metal balloon 38 has aplurality of pores 40 passing therethrough that are in fluid flowcommunication with the annular lumen 42. The first metal balloon 36 hasa solid wall thickness. A bioactive agent, such as a pharmaceuticaldrug, is introduced, into the introductory lumen 46 and passes into theannular lumen 42. The number and size of the plurality of pores 40 aresuch that the bioactive agent and its carrier will not pass through thepores 40 except under the influence of a positive pressure. A fluid,such as a saline solution, is introduced into inflation 44 throughinflation lumen 33, and exerts a positive pressure on first balloon 36which communicates that positive pressure to any bioactive agent presentin annular lumen 42 and second metal balloon 38, and causes dilation ofthe first metal balloon 36 and the second metal balloon 38 and forcesthe bioactive agent in annular lumen 42 to pass through the plurality ofpores 40 in the second metal balloon 38.

[0029] A perfusion metal balloon catheter 50 is illustrated in FIG. 4.The inventive perfusion metal balloon catheter 50 consists generally ofa catheter body member 54 and a metal balloon 52 having a plurality ofperfusion ports 56 passing through the metal balloon. As withconventional perfusion catheters, body fluids, such as blood, flow intoand through the perfusion ports 56 and are perfused with a fluidintroduced through the catheter body member 54.

[0030] Turning to FIGS. 5 and 6 there is illustrated an embodiment ofthe inventive metal balloon catheter 60 in which the surface topographyof the metal balloon 62 is configured to include a plurality oflongitudinal beams or projections 64 that project above the surface ofthe metal balloon 62. By providing the projections 64, the mechanicalproperties of the metal film comprising the metal balloon 62 are alteredto create relatively stronger regions along the longitudinal axis of theprojections 64 and relatively weaker regions intermediate adjacent pairsof projections 64. In this configuration, the relatively weaker regionscreate fold lines for the metal balloon 62 during inflation anddeflation of the metal balloon 62. Alternatively, the surface topographyof the metal balloon may be configured in such as manner as to providethe projections 64 in a pattern that corresponds to the geometricpattern of an implantable device, such as a stent, such that theimplantable device is capable of nesting on the metal balloon 62 betweenthe projections 64 during endoluminal delivery.

[0031] Finally, with reference to FIG. 7, there is illustrated anembodiment 70 of the inventive metal balloon catheter in which the metalballoon 72 is coated with an ultra thin coating of a biocompatibleelastomer 74. Elastomer 74 adds a compliant component to the metalballoon 72 and serves to encapsulate the metal balloon and protectagainst fragmenting in the event of metal fatigue and/or cracking of themetal balloon 72.

[0032] In accordance with the method of the present invention, vacuumdeposition methods as are known in the microelectronics andnano-fabrication arts are preferably employed. It is preferable toemploy sputtering or ion beam-assisted evaporative deposition to depositat least one metal film of a biocompatible metal onto a sacrificialcylindrical substrate. The sacrificial cylindrical substrate has ageometry corresponding to the geometry desired for the inventive metalballoon, and at least one of a plurality of metal film layers aredeposited onto the sacrificial cylindrical substrate. After depositing afilm having a desired thickness between 0.1 μ m and 25 μm, the substrateand the deposited film are removed from the deposition chamber and thesacrificial substrate is removed by means suitable for the selectedsubstrate. For example, a copper substrate may be employed, thensacrificially removed by chemical etching. Any patterning of nestingregions for a stent and/or projections for creating fold lines for theballoon may be imparted either by depositing metal species through amask or by etching regions of a deposited film. The entire metal balloonor selected regions of the metal balloon may be subject topost-deposition annealing to alter the crystalline structure of themetal film and effect changes in the material properties of the metalfilm, such as altering the transition temperature of the annealedregions as well as to create advantageous zero stress-strainconfigurations such as low profile folds.

[0033]FIGS. 8 and 9 illustrate the inventive metal balloon catheterfabricated by sputter depositing nickel-titanium alloy onto a coppermandrel, etching the copper mandrel to release the deposited metalballoon, and adhering the metal balloon onto a polymeric catheter bodyusing a cyanoacrylate biocompatible adhesive to attach proximal anddistal portions of the metal balloon.

[0034]FIGS. 10A-10D depict the inventive metal balloon 110 in itsinflated state (FIG. 10A) having proximal 112 and distal 114 tapersections and an intermediate enlarged tubular section 118. In accordancewith one embodiment of the invention, the metal balloon 110 may beimparted with an deflated geometry as depicted in FIG. 10B in which theintermediate section 118 and the proximal 112 and distal 114 tapersections deflate to form a configuration with a plurality of leaflets120 that project radially outwardly from the longitudinal axis of themetal balloon 110. FIG. 10C is an end view of FIG. 10B. FIG. 10D depictsfolding of the leaflets 120 in order to accommodate endoluminal deliveryor removal of the metal balloon 110.

[0035] The deflated geometry depicted in FIG. 10B may be imparted by awide variety of means, including, without limitation, shape memory orsuperelastic properties of the metal material, fold or score lines alongthe metal balloon 110 defining fold regions for the leaflets 120, orthickened regions of the metal balloon 110 intermediate the leaflets 120that offer greater resistance to folding upon deflation of the metalballoon 110.

[0036] In accordance with the preferred embodiment of fabricating theinventive microporous metallic implantable device in which the device isfabricated from vacuum deposited nitinol tube, a cylindricaldeoxygenated copper substrate is shaped into a geometrical configurationcorresponding to an inflated angioplasty balloon having proximal anddistal tapers. The substrate is mechanically and/or electropolished toprovide a substantially uniform surface topography for accommodatingmetal deposition thereupon. A cylindrical hollow cathode magnetronsputtering deposition device was employed, in which the cathode was onthe outside and the substrate was positioned along the longitudinal axisof the cathode. A cylindrical target consisting either of anickel-titanium alloy having an atomic ratio of nickel to titanium ofabout 50-50% and which can be adjusted by spot welding nickel ortitanium wires to the target, or a nickel cylinder having a plurality oftitanium strips spot welded to the inner surface of the nickel cylinder,or a titanium cylinder having a plurality of nickel strips spot weldedto the inner surface of the titanium cylinder is provided. It is knownin the sputter deposition arts to cool a target within the depositionchamber by maintaining a thermal contact between the target and acooling jacket within the cathode. In accordance with the presentinvention, it has been found useful to reduce the thermal cooling bythermally insulating the target from the cooling jacket within thecathode while still providing electrical contact to it. By insulatingthe target from the cooling jacket, the target is allowed to become hotwithin the reaction chamber. Two methods of thermally isolating thecylindrical target from the cooling jacket of the cathode were employed.First, a plurality of wires having a diameter of 0.0381 mm were spotwelded around the outer circumference of the target to provide anequivalent spacing between the target and the cathode cooling jacket.Second, a tubular ceramic insulating sleeve was interposed between theouter circumference of the target and the cathode cooling jacket.Further, because the Ni—Ti sputtering yields can be dependant on targettemperature, methods which allow the target to become uniformly hot arepreferred.

[0037] The deposition chamber was evacuated to a pressure less than orabout 2-5×10⁻⁷ Torr and pre-cleaning of the substrate is conducted undervacuum. During the deposition, substrate temperature is preferablymaintained within the range of 300 and 700 degrees Centigrade. It ispreferable to apply a negative bias voltage between 0 and −1000 volts tothe substrate, and preferably between −50 and −150 volts, which issufficient to cause energetic species arriving at the surface of thesubstrate. During deposition, the gas pressure is maintained between 0.1and 40 mTorr but preferably between 1 and 20 mTorr. Sputteringpreferably occurs in the presence of an Argon atmosphere. The argon gasmust be of high purity and special pumps may be employed to reduceoxygen partial pressure. Deposition times will vary depending upon thedesired thickness of the deposited tubular film. After deposition, theplurality of microperforations are formed in the tube by removingregions of the deposited film by etching, such as chemical etching,ablation, such as by excimer laser or by electric discharge machining(EDM), or the like. After the plurality of microperforations are formed,the formed microporous film is removed from the copper substrate byexposing the substrate and film to a nitric acid bath for a period oftime sufficient to remove dissolve the copper substrate.

[0038] While the present invention has been described with reference toits preferred embodiments, those of ordinary skill in the art willunderstand and appreciate that variations in materials, dimensions,geometries, and fabrication methods may be or become known in the art,yet still remain within the scope of the present invention which islimited only by the claims appended hereto.

What is claimed is:
 1. A balloon catheter comprising an inflatableballoon consisting essentially of at least one metal.
 2. The catheteraccording to claim 1, wherein the at least one metal is selected fromthe group consisting of titanium, vanadium, aluminum, nickel, tantalum,zirconium, chromium, silver, gold, silicon, magnesium, niobium,scandium, platinum, cobalt, palladium, manganese, molybdenum and alloysthereof.
 3. The catheter according to claim 1, wherein the inflatableballoon has a wall thickness between about 3 μm and 10 μm.
 4. Thecatheter according to claim 1, wherein the inflatable balloon deflatesunder the influence of at least one of a shape memory, superelastic orelastic property of the at least one metal.
 5. The catheter according toclaim 1, further comprising a catheter body fabricated from a materialselected from the group consisting of polymers and metals.
 6. Thecatheter according to claim 1 made by the method comprising the stepsof: vacuum depositing a film of the at least one metal onto thegenerally cylindrical mandrel having a geometry desired for theinflatable balloon to form the inflatable balloon; and removing thegenerally cylindrical mandrel from the formed inflatable balloon.
 7. Thecatheter of claim 1, further comprising a catheter body member having aninflation lumen and at least one inflation port, wherein the at leastone inflation port is in fluid flow communication with an inflationlumen of the inflatable balloon.
 8. The catheter of claim 1, wherein theinflatable balloon is formed of plural layers of the at least one metal.9. The catheter of claim 1, wherein the inflatable balloon furthercomprises a plurality of perfusion ports passing through the inflatableballoon and facilitating fluid flow communication between outside andinside the inflatable balloon.
 10. The catheter of claim 1, wherein theinflatable balloon further comprises a plurality of generally linearprojections emanating from an exterior surface of the inflatable balloonand extending along a longitudinal axis thereof.
 11. The catheter ofclaim 10, wherein adjacent pairs of generally linear projections definefold lines for the inflatable balloon.
 12. The catheter of claim 10,wherein the longitudinal projections form a geometric pattern that isphysically complementary to an implantable device that rests on theinflatable balloon and is delivered by the catheter.
 13. The catheter ofclaim 1, wherein the at least one metal is comprised of a radiopaquemetal.
 14. The catheter of claim 1, further comprising a coating ofbiocompatible elastomer encapsulating the inflatable balloon.
 15. Thecatheter of claim 1, wherein the inflatable balloon has conductiveproperties for transmitting energy delivered from an external source.16. A catheter for localized delivery of a bioactive agent comprising adrug-eluting balloon having a first balloon and a second balloon, havinga plurality of pores passing therethrough, concentrically positionedover the first balloon in a spaced apart relationship defining anannular lumen therebetween, at least one pharmacologically active agentdisposed within the annular lumen and elutable through the secondballoon, each of the first and second balloon consisting essentially ofat least one metal.
 17. The catheter of claim 16, further comprising aninflation lumen and an inflation port, the inflation port being in fluidflow communication between the inflation lumen and the first balloon.18. The catheter of claim 17, further comprising an introductory lumenin fluid flow communication with the annular lumen such that apharmacologically active agent may be introduced into the annular lumenthrough the introductory lumen.
 19. The catheter of claim 16, whereinthe plurality of pores are dimensioned to permit elution of the at leastone pharmacologically active agent only upon application of a positivepressure to the first balloon.
 20. The catheter according to claim 16,wherein the at least one metal is radiopaque.
 21. The catheter accordingto claim 16, wherein the at least one metal is selected from the groupconsisting of titanium, vanadium, aluminum, nickel, tantalum, zirconium,chromium, silver, gold, silicon, magnesium, niobium, scandium, platinum,cobalt, palladium, manganese, molybdenum and alloys thereof.
 22. Thecatheter according to claim 16, wherein the first balloon and the secondballoon have wall thicknesses between about 3 μm and 10 μm.
 23. Thecatheter according to claim 16, wherein both the first and secondballoons deflate under the influence of at least one of a shape memory,superelastic or elastic property of the at least one metal.
 24. Thecatheter according to claim 16, further comprising a catheter bodyfabricated of a material selected from the group consisting of polymersand metals.
 25. The catheter according to claim 16 made by the methodcomprising the steps of: vacuum depositing a first film of metal onto agenerally cylindrical mandrel having a geometry desired in the firstballoon to form the first balloon; depositing a sacrificial layer ontothe surface of the first balloon to assume the desired geometry for thesecond balloon; vacuum depositing a second film of metal onto thesacrificial layer to form the second balloon; and removing the formedfirst and second balloon by eliminating the sacrificial layer andreleasing the formed first and second balloon from the generallycylindrical mandrel.